close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2408791

код для вставки
Oct. 8, 1946.
H. MAGNUSKI
2,408,791
RADIO COMMUNICATION SYSTEM
Filed June 21, 1945aI
.wo“2532...5;..
3, Sheets-Sheet 1
2»
TS
BL.
3.Ai4<IB:m]lu%2ras.d?‘g
.3 ,
532.8:%
mun;_mhm ELa.
U
INVENTOR.
HENRY MAGNUSK]
.2HMREE
.
ATTORNEY
Oct- 3, 1946-
2,408,791
H. MAGNUSK!
RADIO COMMUNICATIGN SYSTEM
Filed “June 21, 1943‘
s Sheets-Sheet 2
P5
1u5m2._3oz4
(1.8%
51W.
v2. .
82:2: mlEHi4o1.: “,.97!3.
__=2:
. 28.
0
3
m3
. v.. .v
0
.053
3v
812.5%:
o
A.
§v
3SQ.@28umm4:3m5:8
mokpqzimEowa
INVENTOR
HENRY MAGNUSKI
743444“
ATTORNEY
Oct. 8,1946.
H, MAGNUSKI
I
2,408,791
RADIO COMMUNICATION SYSTEM
Filed June 21, 1943
3 Sheets-Sheet 5
EGTIFIER 33
B REAGTANCE
MODULATOR I3
> FIG.5
RELATNE DISCRMINATOR
OUTPUT VOLTAGE
20
T
IO
\
I INVENTOR.
-|o .
.
_
HENRY
_
2
o
.
l
2
a
RELATIVE F- u VOLTAGE mvur m
.
MIGROVOLTS AT ANTENNA GROUND
GIR- I9.
7
BY
4
,
MAGNUSKI
_
-
W
,~ ATTORNEY
,
2,408,791
Patented Oct. 8, 1946
UNITED STATES PATENT OFFICE
RADIO COMMUNICATION SYSTEM
Henry Magnuski, Chicago, 111., assignor to Galvin
Manufacturing Corporation, Chicago, 111., a
corporation of Illinois
Application June 21, 1943, Serial N 0. 491,651
,
.
9 Claims.
1
(Cl. 250-43)
2
.
mediate frequency section of the receiving chan
The present invention relates to improvements
nel during signal reception.
in radio communication apparatus and more par
According to a further object of the invention,
ticularly to improvements in combination radio
the modulator stage of the transmission’ channel
transmitter and receiver systems of the charac
is controlled by a variable bias derived from the
ter used. in police and military communication
receiving channel in order automatically to con
work, for example.
trol the carrier frequency of asignal carrier tra
Complete self-contained combination transmit
versing the intermediate frequency section of the
ter and receiver units, both of the portable and
receiving channel during signal reception.
I
?xed position types, are now extensively used in
many forms of radio communication work and 10 It is another object of the invention to provide
improved facilities whereby the system may be
are'especially useful in two-way police and mili
utilized for'signal transmission and reception at
tary communication work. Such units must of
the same carrier frequency without» altering the
necessity be rugged, light in- weight, and easily
tuning of any of the tunable stages of the system.
manufactured in production quantities at low
It is a further object of the invention to pro
cost. They must also be capable of being easily
vide an improved radio transmitter wherein two
and rapidly conditioned to ‘operate either as a
Oscillators arranged in tandem are utilized to pro
transmitter or as a receiver, and should be eas
duce for radiation a signal modulated carrier.
ily tunable to’ transmit or receive at any desired
According to a further object of the invention,
carrier frequency within an allotted frequency
band. Other requirements of a unit of this type 20 the transmission channel is provided with a mixer
stage which follows the master carrier producing
are that the unit have sufficient signal radiating
oscillator and utilizes a crystal oscillator having
power and sufficient sensitivity of reception to
a resonant frequency equaling the‘ center inter
permit high quality two-way communication to
mediate frequency of the ?rst intermediate fre
be held over substantial distances, and that the
quency section of the receiving channel to obtain
receiving channel of the unit be capable of main
the desired frequency of carrier radiation.
taining its sensitivity. in receiving a signal car
It is a still further object of the invention to
rier having a drifting carrier frequency.
provide an improved arrangement for selectively
In general, it is an object of the present inven
tion to provide an : improved combination radio
transmitting and receiving system which meets
I all of the ‘requirements outlined above in a high
l'y satisfactory manner.
It is another object of the invention to provide
a system of the frequency modulated type which
meets all of the requirements outlined above.
It is a further object of the invention to provide
a combined transmitting and receiving system in
which porticnsof both the transmission and. re
ceiving channels are used both during signal
transmission and signal reception, thereby to
minimize the number of component parts of the
system without sacri?cing. desirable operating
features.
'
'
.
According to another object of the. invention, a
combination frequency modulated transmitting
and receiving'syste'mi is provided which'includes
' rendering the transmission and receiving chan
nels active and inactive in a manner such that all
of the facilities mentioned above are selectively,
automatically and appropriately rendered active
and inactive as the two channels are selectively
conditioned for signal transmission and signal re
ception.
The invention, both as to its organization and
method of operation, together with further ob
jects and advantages thereof,- will best be under
stood by reference to the following speci?cation
taken in connection with the accompanying
drawings, in which:
Figs. 1 and 2, when laid end to end in the order
named, illustrate a combined frequency modu
lated radio transmitting and receiving system
characterized by the features of the invention
briefly referred to above;
-
_
a receiving channel of the superheterodyne type,
and in which. improved facilities are provided for
utilizing one of the oscillators of the transmis
Fig. 3 diagrammatically illustrates the circuit
arrangement of the cathode heaters of the elec
tron discharge tubes included in the system
sion channel as a local‘ oscillator'at a mixer stage
shown in Figs, 1 and 2;
v
-
Fig. 4 is a graph illustrating the noise and sig
of the receiving channel during signal reception.
nal response characteristics of the receiver; and
In accordance with a further object of them
Fig. 5 is a circuit diagram illustrating a modi
vention,v improved facilities are provided for uti
?cation of the receiving equipment forming a
lizing a portion of the transmission channel to
obtain automatic frequency control in the inter 55 part of the system'shown in, Figs. 1 and 2.
2,408,791
4
Referring now more particularlypto Figs. 1 and
2 of the drawings, there is illustrated, partially
in schematic form, a combination frequency mod
ulated radio transmission and receiving system
inductance element 42 and a phase shifting net
work which includes the condenser 3'|a and the
resistor 311). A suitable grid condenser 44 shunted
by a grid leak resistor 43 is serially included in the
which is well adapted for use as a complete port Cl input circuit of the oscillator tube M for the pur
able unit and includes a transmitting section Ii)
pose of maintaining the control grid of this tube
and a receiving section II commonly coupled to
at the proper operating potential with respect to
an antenna ground circuit l9 through a tunable
the cathode of the tube.
antenna circuit I8. Brie?y considered, the trans
The signal modulated carrier voltage developed
mitting section | 0 comprises a combination auto
10 across the tunable frequency determining circuit
matic frequency control and reactance modulator
stage I3, a tunable master oscillator M, a tunable
frequency doubler network IS, a tunable trans
4| is impressed between the input electrodes of a
tube 41 included in the frequency doubler |5
through a network which comprises the coupling
mitter mixer I6, a power ampli?er l1, and the
condenser 49 and a resistor 48. This tube is pro
tunable antenna circuit Hi, connected in tandem 15 vided at its output side with a tunable frequency
in the order named. The receiving section II of
selective circuit 52, which includes a ?xed in
the system comprises the tunable antenna cir
ductance element 52a shunted by a ?xed tuning
cuit I8, a tunable radio frequency ampli?er 20,
condenser 52b and an adjustable tuning con
a ?rst mixer or converter stage 2|, a ?rst inter
denser 520, and is tuned to a center frequency
mediate frequency ampli?er 22, a second mixer 20 substantially twice the center resonant frequency
or converter stage 23, a second intermediate fre~
of the frequency determining network 4| forming
quency ampli?er 24, a ?rst limiter 25, a second
a part of the master oscillator stage l4. Anode
limiter 26, a frequency discriminator 21, an audio
current is supplied to the tube 4‘! through a ?lter
frequency ampli?er 28, and a loud speaker 29, all
resistor 54 and the inductance element 52a, and
connected in cascade in the order named. As 25 the usual direct current isolating condenser 5211
pointed out below the system may be selectively
is provided in the circuit 52 to isolate the anode
current path from ground.
In accordance with the present invention, the
set to operate as a receiver. In order to render
carrier voltage developed through operation of
the audio section of the receiving channel H in 30 the tunable master oscillator l4 and the tunable
operative to pass noise signals appearing in this
frequency doubler I5 is utilized as a heterodyning
channel during intervals when a desired signal
frequency source for converting a received fre
is not being received, muting or squelch apparatus
quency modulated radio frequency carrier into a
is provided which comprises a high pass ?lter
correspondingly modulated intermediate fre
controlled to operate either as a transmitter or a
receiver and, when conditioned for operation, is
network 33 coupled to the output side of the fre
quency discriminator 21, a noise ampli?er and
recti?er 3|, a direct current ampli?er 32 and a
muting oscillator and recti?er section 33. These
quency carrier in the ?rst mixer stage 2| of the
receiver channel ll. When, therefore, it is de
sired to utilize the system to transmit and re
ceive signals at a ?xed and preestablished carrier
stages are connected in tandem in the order
frequency without altering the tuning of the
named, and respond to noise voltages appearing
tunable circuits in the system incident to a
change from transmission to reception, or vice
versa, it is necessary to increase or decrease the
in the receiver channel to impress a blocking bias
voltage upon the audio ampli?er 28 in the manner
c explained below.
More speci?cally considered, the transmitting
section of the system comprises a microphone |2
which is arranged to impress audio frequency
voltages developed during operation thereof be
tween the input electrodes of the combination
frequency control and modulator tube 38 through
a. coupling network which comprises a microphone
transformer 35, a condenser 36, and a resistor
31. The space current path through the tube 38
is connected in shunt with the space current path
through the tube 40 of the master oscillator l4,
and also shunts the tunable frequency deter
mining circuit 4| of the master oscillator M. This
oscillator is of the conventional tuned plate cir
cuit type, the frequency determining circuit 4|
thereof comprising a, ?xed inductance element
4|a which is tuned to the desired resonant fre- _
quency by means of the shunt connected ?xed
‘condenser MI) and an adjustable tuning con
denser 4|c, Operating potentials are supplied to
the anodes of the tubes 40 and 38 through a re
sistor 46 and the inductance element 4|, a low
impedance direct current blocking condenser 4|d
being provided in the tunable circuit 4| in order
to isolate this direct current path from ground.
The tunable frequency determining circuit 4| of
the ‘oscillator I4 is regeneratively coupled to the
input electrodes of the tube 40 by means of an
inductance element 42 which is inductively
coupled to the inductance element 4|. It is also
coupled to the input electrodes of the frequency
control and modulator tube 38 by means of the
output frequency of the frequency doubler |5 by
an amount equal to the value of the intermediate
frequency utilized in the ?rst intermediate fre
quency ampli?er section 22 of the receiver chan
nel ||. Whether or not the output frequency of
the doubler I5 is raised or lowered to provide the
desired frequency of carrier transmission, will of
course depend upon whether the doubler output
frequency is above or below the particular car
rier frequency at which transmission is to be ef
fected. In the particular arrangement illustrat
ed, a piezoelectric crystal 58 having a resonant
frequency equal to the intermediate frequency
utilized in the ?rst intermediate ampli?er 22 of
the receiver is utilized to increase the frequency
of a transmitted signal carrier above the carrier
frequency appearing across the frequency selec
tive circuit 52 by an amount equal to the inter
mediate frequency utilized in the ?rst intermedi
ate frequency ampli?er 22. More speci?cally
considered, the tunable circuit 52 is coupled to
the input electrodes of the transmitter mixer
. tube 63 through the shunt connected crystal 58
and condenser 59.‘ A grid leak and condenser
network comprising the two resistors 55 and 56
‘and a condenser 51 is provided for maintaining
the proper bias potential between the input elec
trodes of the mixer tube 63. For the purpose of
driving the crystals 58 to maintain oscillation of
the crystal at its resonant frequency, a tuned cir
cuit 60 is provided which is suitably designed to
resonate at the same frequency as the crystal 58
and comprises a ?xed condenser 60a shunted by
2,408,791
6
an adjustable inductance element 691). This net
work is included in the screen electrode circuit ‘of
the mixer tube 63‘ and also in the path compris
ing the resistor 62 over which, the required. oper
ating potential is positively applied to the screen
electrode of the tube 63.
.
The mixer tube 63 is provided with a tunable
frequency selective output circuit 64, which com
prises a ?xed inductance element 64a shunted ‘by
and- screen electrodes. of the tube. This crystal
‘has a resonant frequency of 6.815 megacycles
which is greater than the intermediate frequency
utilized inthe ?rst intermediate frequency am
pli?er ZZ-by'an amount equal to the intermediate
frequency utilized in the second intermediatefre
quency ampli?er 23; A suitable biasing network
comprising the series connected resistors 18a and
18b shunted by thegrid condenser 19 is provided '
the ?xed condenser 64b and the adjustable tun 10 between the input electrodes of the tube ‘Hiv for
maintaining, the ‘proper bias voltage between these
ing condenser 640 through the low impedance
electrodes.
direct current isolating condensers 64d and- Me.
Noise and signal voltages appearing at the out
This circuit is normally‘ maintained tuned to a
put side of the second. limiter 2B are introduced
frequency'which is equal to twice the output fre
quency of the oscillator I4 plus the resonant fre—. 15 into the frequency discriminator 21. Brie?y con
sidered, this discriminator comprises a tuned
quency of the crystal 58‘, which latter frequency
circuit 8-1,. a pair of diode recti?er tubes ‘88 and
equals the ?rst intermediate frequency used in
89, the space current. paths of which are re
the receiver channel I l-. The output voltage ap
spectively shunted by load resistors 90 and 9|,
pearing across the circuit. 64 is impressed across
the input circuit of the power ampli?er I] 20' a radio frequency‘ by-pass condenser 93 having
substantially negligible‘ impedance to frequencies
through a coupling network which includes the '
condenser 65.
,
7
of the order of. the second intermediate frequency,
and a stabilizing condenser 92. More speci?cally,
the resonant circuit 81 serves to tune the‘ fre
stage 2| is illustrated as being resistance-capaci 25 quency discriminator network to a center fre
quency equal to‘ the second intermediate fre
tance coupled to the output circuit of the tunable
quency and comprises a pair of series connected
radio frequency ampli?er 20 through a network
condensers 81b and 810 which are shunted by
which includes the coupling condenser 68 and re
an adjustable inductance element 81a. Prefer‘
sister 69. As indicated above, when the system
is conditioned for reception, the tunable master 30 ably the last mentioned element is of the variable
permeability type being provided. with an adj ust
oscillator l4 and the tunable frequency doubler
able powdered ferrous metal core, the position of
I5 are utilized as a heterodyning frequency source
which may be changed. to alter the inductance
required to effect the desired carrier frequency
of the element within the desired limits; The
conversion in the ?rst mixer stage 2|; To this
end, an inductance element 53 which is induc 35 circuit constants of the resonant circuit '81 are so
chosen that the discriminator network is pro
tively coupled to the inductance element 52a of
vided with a band pass characteristic such that
the frequency selecting circuit 52 is included in
all desired signal components of a‘. frequency mod
the cathode-ground circuit of the mixer tube 19.
ulated carrier appearing in the second interme
_ The output electrodes of this tube: are coupled to
a ‘?xed tuned frequency selecting circuit 1 IV which‘ 4.0 diate frequency channel 24, 25, 26 may be de
tected and impressed upon the input circuit of
comprises a ?xed condenser 'Hb shunted by an’
the audio» ampli?er 28. The voltage appearing
adjustable inductance element ‘Ha andis tuned
across the. output side of the second limiter 26 is
to the desired ?rst intermediate frequency of 4.3
impressed upon the discriminator network 21
megacycles, for example. Anode potential is
through a coupling condenser'86 which is con
supplied to the tube 10 over a path which in
nected' at one. side thereof to the junction point
cludes the inductance element 'Hu' and a. ?lter
between the two condensers 81b and 81c. Audio
resistor ‘l3 which is shunted by a by-pass ‘con
frequency voltages detected through operation of
denser 12. The tuned output circuit ‘H of the
the discriminator 21' appear across the condenser
tube 19 is coupled to the input electrodes» of the
9:3: and are impressed: upon the input side of the
?rst tube in the intermediate frequency ampli?er audio. frequency ampli?er 28 through a coupling
22. through a network which comprises the cou
circuit which includes radio frequency decoupling
pling condenser 14 and resistor 15.
resistor 94, an audio frequency ?lter comprising
The output side of the ?rst intermediate‘ fre
the resistor 95 and condenser 96', an audio fre
quency‘ ampli?er 22 is coupled to the input elec
quencycoupling condenser 91, and a volume con
trodes of the mixer tube 16 provided at the sec
trol voltage dividing network comprising the two
ond mixer or converter stage 23 in an obvious
resistors '99 and H10 and a direct current block
manner. This tube is provided with output elec
ing condenser HH. It will be understood in this
trodes which are bridged by a frequency selec
regard that, the proportion of the available audio
tive circuit 8'! tuned to the second intermediate
frequency of 2.515 megacycles, for example, and _ 00 frequency voltage appearing across the series con
nected; resistors 98* and I90» which is impressed
comprising a condenser 81b shunted by an ad- ‘
upon the input circut of the audio frequency am
justable inductance element 8H1. Anode poten
pli?er 28,>is determined by the setting of the wiper
tial is supplied to the tube 16 over a path which
99 'aiong the‘ resistor 98.
'
includes the inductance element 8m and a ?lter
As will be explained more fully below, noise sig
resistor 83 shunted by a by-pass condenser 82.
nal's. appearing in the signal transmission chan
The voltage appearing across the frequency'se
nel of the receiver in the absence of a received
lective circuit 8| is impressed across the input
signal modulatedcarrier are passed through the
side of the second intermediate frequency ampli
Referring now more in detail to the signal re
ceiving channel Hv of the system, the ?rst mixer
?er 24 through a network which comprises the a
coupling condenser 84v and a resistor 85. For the '‘
purpose of effecting the required carrier fre
quency conversion at the second mixer stage‘v 23,
the miXer tube 19 is provided with an oscillator
section of the Pierce type which includesa piezo-v
electric crystal 71 connected. between the control
discriminator 21- and appear as detected audio
voltages across the condenser 93'. Such detected
voltages are impressed across the high pass ?lter
network 30, and. those components thereof‘ hav
- ing. frequencies» above the cutoff frequency of the
?lter network‘ are impressed between the input
electrodes of the tube [96 included in noise ann
2,408,791
7
8
pli?er and recti?er 3I. More speci?cally consid
ered, the high pass ?lter 30 comprises avpair of
series condensers I01 and I02 and a pair of
diode 88, are of the ?lamentary cathode type.
The diode recti?er 88 must of necessity be of the
indirectly heated cathode type since the cathode
thereof is,vduring operation of the discriminator
2‘I, maintained at potentials substantially above
the reference ground potential present upon the
shunt resistors I03 and I00, and is designed to
pass those components of noise voltages which
have frequencies above the normal signal re
producing band of the receiver. The noise am
pli?er section of the tube I00 works into a noise
recti?er circuit which comprises the diode sec
tion of the tube and a. load resistor IIO.
?lamentary cathodes of the remaining tubes pro
vided in the system. More speci?cally, the circuit
arrangement of the cathodes provided in the var
This 10 ious electron discharge tubes referred to above
and also provided in the diagrammatically illus
recti?er circuit is coupled to the anode of the
tube I06 through a coupling condenser I08 which
trated sections of the system, is shown in Fig. 3
is of appropriate impedance to pass any noise cur
of the drawings. In this circuit, reference char
rents which may be transmitted through the high
acters corresponding to those used in Figs. 1 and
pass ?lter 30. Anode and screen potentials are 15 . 2, but having the differentiating subscripts a and
supplied to the tube I06 through the resistors I01
b, are used to identify the relationship between
and I09, the second of which is by-passed to
the cathodes and the respective associated cir
ground through a condenser‘ III‘.
cuit sections, as shown in Figs. 1 and 2. From
Recti?ed noise voltages appearing across the
a consideration of the circuit arrangement shown
load resistor IIO are utilized to control the bias 20 in Fig. 3, it will be noted that the various cath
between the input electrodes of the tube I I3 pro
odes are effectively isolated at radio and audio
vided in the direct current ampli?er 32. Theini
frequencies by means of the separating ?lter net
tial or threshold bias established between the elec
works comprising the illustrated high impedance
trodes of this tube is derived from a voltage divid
choke coils and the low impedance by-pass con
ing network, which comprises the series connected 25 densers. It will also be noted that current for
resistors IIBa, H61), and H00 bridged across the
energizing the various cathodes in the series
available source of anode potential, and is pro
parallel circuit is supplied by a direct current
vided with a tap II‘I adjustable along the resistor
source I35 through the contacts of a manually
I IE to impress a variable positive potential upon
operable “on” and “off” switch I36. The cath
the control electrode of the tube I I3 through the
odes IBa and Ho of the electron discharge tubes
?lter resistor H5. The biasing circuits connected
respectively provided in the mixer I6 and the
between the input electrodes of the tube II3 are
power ampli?er H are arranged to be energized
by-passed for audio frequency currents by means
in series with each other and with a suitable cur
of a condenser I I4. Screen and anode potentials
rent limiting resistor I31 through the contacts of
are applied to the ampli?er tube I I3 through the 35 a manually operable “press-to-talk” switch I38.
resistor H8 and the resistors H6 and I I9, in
This switch is normally spring biased to its open
series, respectively.
circuit position and may be utilized in the man
The direct current ampli?er 32 as controlled
ner explained below selectively to condition the
by the variable bias voltage derived from the
system for signal transmission or signal reception,
load resistor I I 0, is utilized to control the starting 40 as desired. It is provided with a pair of normally
and stopping of the muting oscillator and recti?er
open contacts I38a which are closed to connect
33. This stage of the muting or squelch appa
the microphone I2 across the primary winding
ratus comprises a dual purpose tube I20 having
of the transformer 35 only when the switch is
an oscillator section which includes a tuned fre
operated to condition the system for signal trans
quency determining circuit I2I connected be
» mission. From an inspection of the cathode cir
tween the output electrodes of the tube through
cuit arrangement, it will be apparent that this
a by-pass condenser I22. The resonant circuit
circuit has been carefully arranged to utilize the
'I2I is ?xed tuned to a particular frequency of
voltage drops across certain of the cathodes as
from 200 to 300‘ kilocycles and comprises an in
bias voltages between the input electrodes of cer
ductance element I2 Ia shunted by a tuning con
tain of the other tubes provided in the system.
denser I2 I12. It is regeneratively coupled to the
For example, the voltage drop appearing across
input electrodes of the tube I20 by means of a
the cathode 25a of the tube provided in the ?rst
feed back circuit which comprises an inductance
limiter stage 25 is impressed between the ?la
element I23 inductively coupled to the inductance
mentary cathode I5a of the tube 4'‘! in the proper
element I2 Ia and connected in series with ‘a par 55 direction to bias this cathode positively with re
allel connected grid leak resistor I24 and con
spect to the control grid of the tube. These bias
denser I25 between the control grid and cathode
voltages, as derived from the circuit network
of the tube I20. Anode potential is supplied to
shown in Fig. 3, are appropriately indicated in
the tube I20 over a path which includesthe in
Figs. 1 and 2 of the drawings by the illustrated
ductance element I2Ia and a resistor I26. The
battery symbols, and the relationship between the
oscillator section of the tube I20 is coupled to the
respective battery symbols and the voltage drops
rectifying circuit of the tube through a coupling
across certain of the cathodes shown in Fig. 3
condenser I29, and the indicated rectifying cir
will be readily apparent from a careful compari
cuit serially includes the diode recti?er section of
son of the circuit shown in Fig. 3 with that shown
the tube and the resistors I28, I32 and 102;. Any 55 in Figs. 1 and 2.
bias voltage appearing across the load resistors
Preferably, the transmitter mixer tube 03 is
I28, I32 and 'I8b'during operation of the oscil
a pentode of the well known commercial 3A4.
lator and recti?er stage 33 is negatively applied
type, the frequency doubler tube 4'! and the mas
to the control grid of the ?rst tube in the audio
ter oscillator tube 40 are commercial type 1T4
frequency ampli?er 28 over a path which com 70 pentodes, the automatic frequency control and
prises the resistor I21, the resistor I00 and the
reactance modulator tube 38 and the ?rst mixer
lower portion‘of the resistor 98.
tube ‘I0 are commercial type 1L4 pentodes, the
In order to insure that the system will operate
second mixer tube ‘I5 is a commercial type 1R5
efficiently with low battery current‘ drain, all of
pentagrid converter, the two diodes 80 and 89
the tubes, with the exception of the discriminator 75 are of the commercial type 1A3 and 155, respec
2,408,791
10
9
plied between the input electrodes of the tube 38
effectively serves to_ vary the tuning of the net
tively, the noise amplifier, and recti?er tube I05
and the muting oscillator and recti?er tube I20
work 4| in like manner, whereby the carrier out
put of the oscillator I4 is reactance modulated
in accordance with the audio signal voltage im
pressed between the‘ input electrodes of the tube
38.’ This modulated carrier‘ voltage is impressed
between the vinput electrodes of the tube 41- of
the frequency doubler I5- through the coupling
muting oscillator and recti?er tube I20 is con 10 condenser 49. Due to the action of the tube 41
in distorting the signal modulated carrier voltage
trolled in the manner more fully explained below
and- the action of the tunable frequency selecting
to effect the desired starting and stopping of the
circuit '52 in selecting only signal modulated car
oscillator section of this tube. It will be under
rier components having twice the frequency of
‘stood that the tuning elements of the various
the carrier voltage developed at the output side
tunable circuits provided in the system are gang
of‘ the oscillator I 4, the modulated carrier voltage
controlled to be operated in unison, so that fre
appearing across the output circuit of the-dou
quency alignment between the various resonant
bler I5 has a ‘carrier frequency which is twice
frequencies thereof is maintained during each
that of the oscillator carrier output frequency,
tuning operation. More speci?cally, the tuning
element of the antenna circuit I8‘, the tuning ele 20 1. e. 40 megacycles in the case assumed above.
The signal modulated carrier voltage appearing
ment of the radio frequency ampli?er 20, and the
across; the frequency selecting circuit 52 is im
adjustable condensers 64c, 52c and Mo, respec
pressed‘ between the input electrodes of the trans
tivelyrprovided at the tunable stages I6‘, i5 and
are commercial type 135 pentodes, and the direct
current ampli?er tube H3 is a commercial type
1L4 pentode. Suitable screen potentials are ap
plied to the tubes 63, 4'1, 40', 38 and 16 over direct
current paths which respectively include the ?lter
resistors 52, 50, 45, 39 and 80, respectively. The
potential applied to the screen electrode of the
mitter mixer tube 63 over a path which includes
I4, are mechanically connected in the manner in
, the coupling condenser 59 and the heterodyning
dicated by the dash line U, so that all of the
piezo-electric crystal 58.» As previously explained,
enumerated tuning elements may be operated in
this crystal has a» resonant frequency which is
unison.
equal to the ?rst intermediate frequency used
Brie?y to consider the operation of the sys
inv the‘ receiving channel II of the system. Ac
tem, it will be understood that when the switch
I36 is operated to its closed circuit position, the 30' cordingly, this. crystal, acting in conjunction with
the tuned circuit 60,. functions to produce a car
cathodes of all tubes provided in the system, with
rier voltage which is electronically mixed in the
the exception of the cathodes I50: and I-"Ea of the
tube 63' with the carrier frequencyoutput across
tubes provided in the mixer ‘I6 and the power am
the tuned circuit 52, so that a carrier is produced
pli?er H, are energized from the current source
I35.
at the output side of the mixer tube 53 having. a
If now the push-to-talk switch I33 is oper
frequency equal to twice the output frequency
of the‘. oscillator I4 plus the ?rst. intermediate
frequency. This carrier voltage is. frequency
modulated in accordance with the audio fre
quency voltage applied to. the. input electrodes of
the modulator tube 38. At theioutput side of the‘
ated to its closed circuit position, the cathodes
16a, and I-‘Ta are also energized. Duevv to the ?la
mentary character of the energized cathodes,
they‘ are rapidly heated‘ to electron emitting tem
peratures following the energization thereof.
When the two switches I35 and I38 are thus
operated, the system is conditioned for signal
transmission at the particular carrier frequency
established by the tuning of the ?ve tunable
stages I4, l5, l6‘, i1 and I181 of the transmission
channel. In this regard it will be understood that
when space current flow through the: tube 45' is
initiated; the master oscillator I4starts to oscil
late ‘at a carrier frequen'cy"which is primarily
determined byv the " setting of the tuning con
tube 63,. this particular signal modulated carrier
voltage is selected throughthe action of the tuned
frequency selecting‘ circuit 64 and is impressed
45
across. the‘ input circuit of the power amplifier I‘!
through the coupling condenser 65. After being
ampli?ed by the ampli?er I1, the voltage is trans
mitted through the tunable antenna circuit I8
50:
and impressed across the antenna ground circuit
t9 for radiation.
,Referring now‘ more speci?cally to the‘ func->
tion performed by the tunable transmitter mixer
I6, it is pointed out abovethat the tunable fre
quency selecting circuit ~64 is tuned to respond
denser 4'I:c. and‘. is. secondarily determined by the
magnitude of the bias voltage between the control
grid and cathode of the tube '38. More generallyv
considered, if the receiving channel II of the
system is designed to operate 'with a first. inter- 55' only to a signal. modulated carrier having a car
rier frequency which is greater than twice the
mediate- frequency of" 4:3 megacyclesl and. signals
output carrier frequency of the oscillator I4-by
are‘to be transmitted and received’ at a. carrier
van
amount equal to the intermediate frequency
frequency: of‘ 44.3 megacycles, the condenser 4'I‘c
utilized inv the ?rst intermediate frequency chan
is so‘ adjusted that with zero bias upon the con
nel 22,0f the receiver. Since the carrier voltage
trol grid of vthe tube: 38, the masterv oscillator I41
appearing across- the’ tuned output circuit 52 of
will produce a carrier voltagehaving a frequency
the frequency doubler‘ I5 is used as a heterodyn
of" 20 megacycles and the other’ tunable. circuits
ing‘ frequency source at‘ the'?rst mixer stage 2i
of the transmission- channel. I'Il‘are adjusted'am
during reception and this frequency is mixed
cordingly. With the frequency of the signal‘ car
I
with
the; frequency produced by the crystal 58 to‘
rier thus determined‘, an audio frequency voltage
produce‘ at frequency of’ carrier radiation which is
developed: through operation of‘- the microphone
equal to the sum of the‘ two frequencies, signal
I2 is impressed‘ through the microphonegtrans
reception and‘ transmission may be held at the
former >3 5' and the coupling condenser 36' between
same carrier frequency. Thus if the crystal 58
the. control grid and cathode of the modulator
tube 38. The resulting audio frequency variation 4 has a’ resonant frequency of 4.3 megacycles, equal
ing the center intermediate frequency used in the
of the voltage between thecontrol grid and cath
?rst intermediate frequency‘ section of the re
ode of the tube 38'. effectively changes thereac
ceiver' channel I I", and the tuning. elements of the
tance of the tunable. frequency determining cir
tunable stages I4, I5, I6, I'I', I8’ and 25 are ad
cuitJ4‘I' of'the master oscillator , I‘4' at a correspond.
ing rate.v In other words‘, varying the voltage ap 75 justed by means of the‘ adjusting element U to'
11
12
a setting wherein the carrier output frequency
of the oscillator I4 is 20 megacycles and the car
rier output frequency of the doubler I5 is 40
megacycles, then the tunable stages ll, [8 and
6‘! to the input side of the tunable radio fre
quency ampli?er 2D. This voltage, as ampli?ed by
29 are tuned to a carrier frequency of 44.3 mega
cycles. This of course means that if the tunable
put voltage is impressed between the cathode and
stages of two remotely located sets of the char
including the inductance element 53. It is thus
acter illustrated are tuned for transmission and
reception at the same carrier frequency, it is
converted into a signal modulated intermediate
As indicated above, the desired increase in the
frequency of the radiated carrier over the carrier
age and of the desired second intermediate fre
quency, appears across the tuned output circuit
the ampli?er 20, is mixed with the carrier output
voltage of the frequency doubler l5, which out
control grid of the tube 10 over a coupling path
frequency carrier which is ampli?ed through the
unnecessary to alter the settings of the tuning 10 ?rst intermediate ampli?er 22 and impressedbe
elements of either set when the direction of trans
tween the input electrodes of the tube 16 pro
mission between the two systems is changed.
vided in the secondmixer stage 23.
Thus, the systems of the two sets may rapidly
In the second mixer stage, the intermediate
be altered for transmission in either direction
frequency carrier output from the ampli?er 22 is
- with a minimum number of manual operations 15 mixed with the carrier frequency produced
on the part of the persons using the respective
through operation‘ of the crystal Tl so that a beat
sets for two-way communication.
frequency carrier, modulated with the signal volt
frequency appearing at the output side of the 20 8|. This modulated carrier, as selected through
frequency doubler I5 is provided through the
the action of the tuned circuit 8|, is transmitted
action of the piezoelectric crystal 58. In con
through the condenser 84 to the second interme
sidering the manner in which this crystal is driven
diate frequency ampli?er 24 where it is ampli?ed
at its resonant frequency, it is pointed out that
and transmitted successively through the limiter
at this resonant frequency, the upper terminal 25 stages 25 and 26 to the input side of the discrim
of the tuned circuit 52 is e?ectively at ground
inator 21. In this discriminator the modulation
potential due to the low impedance of this cir
components of the second intermediate frequency
cuit at the particular frequency in question.
carrier, as represented by deviations in the car
The resonant circuit 39 which is coupled between
rier frequency from the, established center fre
the cathode and screen electrode of the tube 63 30 quency, are detected in the manner pointed out
is precisely tuned to the resonant frequency of
below. The detected signal voltage appears
the crystal 58. Due to the electronic and capaci
across the condenser 93, which condenser is pos
tance coupling between the upper terminal of the
sessed of exceedingly low impedance at the center
tuned circuit 60 and the lower terminal of the
carrier frequency and exceedingly high imped
crystal 58, a su?‘icient driving voltage is applied
ance at audio frequencies. This voltage is im
across the crystal 58 through the tuned circuit
pressed across the voltage dividing network com
52 to maintain the oscillation of the crystal;
prising the resistors 98 and I00 through the car
This coupling also serves to maintain the tuned
rier frequency decoupling resistor 94 and the au
circuit 60 oscillating at its resonant frequency.
dio frequency coupling condenser 91. The por
In order to condition the system for signal 40 tion of this voltage which appears between the
reception after signal transmission has been ef
wiper 99 and ground is impressed across the input
fected in the manner explained above, the push
circuit of the audio frequency ampli?er 28 in an
to-talk switch I38 is released. Incident to the
obvious manner. The audio frequency signal
restoration of this spring biased switch to its
voltage as impressed across the input side of the
normal position, the cathodes lSa and Ila of the 45 audio frequency ampli?er 28 is ampli?ed in this
tube 83 and the tube provided in the power ampli
ampli?er and transmitted to the loud speaker 29
?er H’ are deenergized in an obvious manner.
for reproduction.
Thus, the transmitter mixer stage IB and the
Referring now more particularly to the opera
power ampli?er stage I‘! of the transmitter chan
tion of the discriminator 21, it will be noted that
nel it! are rendered inactive without . in any 50 this circuit is essentially a four terminal bridge
way interrupting or otherwise affecting the oper
circuit two arms of which respectively include the
ation of the preceding stages I3, l4 and I5. In
condensers 87b and 810 of equal capacitances. A
this regard it is pointed out that when space
third arm of the bridge comprises the capacitive
current ?ow through the mixer tube 63 is inter
impedance of the diode 88. l The fourth arm of
rupted, the. operation of the oscillator section 55 the bridge comprises the combined capacitive im
of this tube, i. e. that portion of the tube input
pedance of the diode 89 and the condenser 92.
circuit which comprises the intercoupled crystal
The inductance element 81a is bridged between
58 and resonant circuit 60, is arrested. Thus,
two terminals of the bridge circuit and the fre
no carrier voltage is produced in the transmis
quency modulated. signal voltage is applied to the
sion channel l0 having a frequency approaching
circuit across the other two terminals thereof.
the intermediate frequency used at either the
Since the load resistors 99 and 9| have imped
?rst or second intermediate frequency sections
ances far in excess of the capacitive impedances
of the receiving channel ll. Accordingly, the
of the diode legs of the bridge circuit at the fre
continued operation of the three stages l3, l4
quencies involved, they may be neglected in ana
and I5 of the transmission channel H can in no 65 lyzing the circuit. Again, the capacitance of the
way interfere with the reception of the selected
condenser 93 is so much greater than that of
signal modulated carrier.
'
Assuming that the system is conditioned for
signal reception in the manner explained above,
and that the tunable stages of the system are
appropriately tuned to the center frequency .of
a desired frequency modulated signal carrier, the
signal carrier voltage appearing across the an
either diode leg-Of the circuit, that this condenser
may also be neglected in analyzing the circuit.
With this bridge circuit arrangement the voltage
appearing at the output side of the discriminator
is the difference between the absolute values of
the voltages to ground at the upper and lower
terminals of the inductance element 81a. From
an examination of the bridge, it will be under
tenna ground circuit 19 is transmitted through
the tunable circuit l8 and the coupling condenser 75. stood that if the capacitance of the condenser 81b
22,468,791“
13
equals that of the ‘condenser 810, which it does,
and the capacitances'of the two diode legs of the
circuit are equal, such that the bridge is balanced,
the currents respectively traversing the condens
14
relativemagnitudes of the currents traversing the
circuit-elements 8.‘la,l8~lb and 810 so that the volt
ageb'etween the lower terminal of the inductance
element 87a and ground exceeds that between the
ers 81b and 810 are equal so that equal ‘voltagev Cl upper terminal of the inductance element 81av
and ‘ground. As a result, an output voltage
dropsappear across these condensers. Accord‘
which negative with respect to ground is pro
ingly, no difference between the voltages to
duced ‘between the cathode of the diode 88 and
ground is developed at the upper and lower
ground. It has been found that the extent or
terminals of the inductance element 81a, regard-'
less of the frequency of the exciting voltage ap-~ 10 magnitude of the discriminator output voltage
varies in accordance with the departure of the
plied to the circuit. In the actual circuit, how
exciting frequency from the center intermediate
ever, the capacitance of the leg which includes
frequency to which the discriminator network 21
the diode '89 is greater than the capacitance of
the leg including thediode-88 by an amount equal ' is center tuned. It will be understood, therefore,
that if'the. frequency of the carrierappearing at
to the capacitance value of the condenser 92, such
the output side of the limiter 26 is frequency
that the bridge is unbalanced. Accordingly dur
modulated in accordance with a given audio sig-v
ing excitation of the circuit, the current travers
nal, a corresponding audio frequency .voltage‘is
ing the condenser 81c exceeds the current trav
accurately reproduced across the condenser ~93
ersing the condenser 81b so that a current is
caused to flow through the inductance element 20 at the output side. of the discriminator 2.1.
To consider somewhat more fully the action of
81a.
'
the condenser 92in stabilizing the operation of
The magnitude of this current obviously de
the discriminator network 21, it may be pointed
pends uponthe reactive impedance of the induct
- out that if the impedances of the four legs of the
ance element 81a at the particular frequency of
bridge circuit are perfectly balanced, changes in
excitation, and the direction of current ?ow is
the exciting frequency will not produce the de
such that the voltage drop across the condenser
sired differences of potential between the upper
81b is enhanced and that across the condenser
and lower terminals of the inductance element
810 is decreased. It will be understood, there
81a and ground. By providing the condenser v92
fore,‘ that by suitably proportioning the imped
ance of the inductance element 81a relative to 30 connected in the manner illustrated, however,
thereby to insure that the over-all capacitance
the reactive impedance of the condensers 81b and
between the lower terminal of the ‘inductance ele
8T0. at ‘a particular center frequency to establish
ment. Bid and ground exceeds that between the
a given relationship between the currents trav
upper terminal’ of this element and ground, the
ersingfthe circuit elements 81a, 81b and 8-10, the
desired circulating current within the resonant
absolute voltages between the upper and lower
terminals of the inductance element'illa and,
ground become equal. In their relationship to
each other,,however, these, voltages are out of
phase so that a difference voltage actually exists
between the upper and lower terminals of the I
circuit 81 will always be produced to insure sta
bility of circuit operation. In this regard it is
pointed out that the unbalancing or stabilizing
condenser .92 may be connected either between
the ‘lower terminal of the resonant circuit '81 and
ground/or between the upper terminal of this cir
cuit and ground. In either case, the desired op
eration of the ‘network is produced. It is noted,
however, that when a condenser 92 .of appropriate
ductance element 870. to ground. The particular
frequency at which these absolute voltages be 4-5 capacitance value is connected between the upper
terminal of the circuit 81 and ground, the direc
come ‘equal to balancethe bridge represents the
tion of circulating current flow within the circuit
center frequency at which the 'voltage appearing
is reversed. Accordingly, the polarity of the out
atjthe output side of the discriminator between
put voltage produced across the condenser 93 in
the cathode'of the diode .88 and ground becomes
cident ‘to a given departure of the exciting fre
zero. In'this regard it is pointed out that when
quency from the center intermediate frequency is
the bridge is balanced so that the voltages from
the reverse of that which is obtained for the
the upper and lower terminals of the inductance
same frequency departure when the condenser
element 26a to ground are equal, equal direct
92 is connected between the lowerterminal of the
voltages are produced across the load resistors 99
resonant circuit and ground.
and '91. These voltages'are opposingly'combined
If desired, one rectifying section of the_im
in a direct current path through the inductance
proved discriminator 21. may be combined with
element 81 so that when equal, no direct voltage‘
the audio frequency ampli?er v28 in the manner
appears between the cathode of the diode 88 and
illustrated in Fig. 5 of the drawings, wherein ref
ground.
'
'
erence characters‘ corresponding to those ,used in
As the exciting vvoltage for‘the resonant circuit
Fig. 2 identify the same circuit elements. From
81 is increased above the center ‘frequency, due
an examination of the Fig. 5 arrangement, it will
to the signal 'modulation'thereof at an audio rate,
be seen that the diode section of the tube 89 is
the reactive impedances of the circuit constants
utilized as one of the rectifying paths of the dis
change to alter the relative magnitudes of the
criminator, and that the cathode, anode and
currents traversing the circuit. elements 81a, Bl'b'
three grids of the tube are used to amplify the
and. 810, so that the voltage from the upper ter
circuit 81. rI‘his difference voltage is, of course,v
equal to ‘the vector sum of the absolute voltages
from the ‘upper and lower terminals of the in
minal of ‘the inductance element 81a to v‘ground
exceeds that between the lower terminal of the
inductance element ?lva'and ground." Accord
ingly, a voltage which‘ is positive with respect to
ground is produced between the cathode of the‘
diode 88 vand ground. If, on the other hand, the
exciting frequency for the circuit 81 is vdecreased
audio'frequency voltage which is developed.'be-'
tween the wiper 99 and ground during reception
of a selected signal. This audio voltage is trans
Ymitted to the loud speaker 29 for reproduction
through a coupling transformer I39. The man
ner in which the audio section of the tube is
blocked under the control of the muting oscilla
tor '33 and mode of operation of the discriminator
ances'of the ‘circuit constants change 'to alter‘the 75 21 are exactly the same as ‘explained herein ‘with
below the center frequency, ‘the ‘reactive imped
15
2,408,791
16
reference to the system shown in Figs. 1 and 2.
In fact, the circuit of Fig. 5 may be directly sub
plied to the control grid of the modulator tube
stituted for the discriminator 21 and the audio
quency decoupling resistor 94, the audio frequency
decoupling resistor 95 and the ?lter resistors 13!
frequency ampli?er 28 in the system of Figs. 1
38 over a path which includes the radio fre
and 2 to perform in the same manner, when the Cl and 31. At this point it is noted that the audio
indicated connections are made between this cir
frequency ?lter comprising the decoupling re
cuit and the limiter 28, the high pass ?lter 38,
sistor 95 and the by-pass condenser 96 prevents
the transmitter mixer [8, the muting oscillator
and recti?er 33, and the modulator stage I3.
the'audio ‘frequency components of the voltage
appearing at the output side of the discriminator
10 21 from being impressed between the input elec
Automatic frequency control
trodes ‘of the modulator tube 38. This ?lter also
prevents audio frequency voltages developed dur
As previously indicated, provisions including
ing signal transmission by the microphone l2
the discriminator 21 and the modulator stage [3
from being impressed upon the input side of the
of the transmission channel ID, are made in ac
cordance with the present invention for automat 15 audio frequency ampli?er 28 through the coupling
condenser 91.
ically adjusting the output frequency of the fre
As the bias applied to the tube 38 increases, the
quency doubler [5 so that the difference between
magnitude of the out of phase current component
this frequency and the center frequency of a se
traversing the space current path of the mod
lected carrier is held at a substantialy constant
value which substantially equals the center in 20 ulator tube 38 and the tuned circuit 4| changes
so that the frequency of the voltage developed
termediate frequency to which the resonant cir
by the master oscillator 14 increases. As this
cuits of the ?rst intermediate frequency section
frequency increases, that appearing at the out
of the receiving chanel II are tuned. The pur
put side of the doubler l5 obviously changes in
pose of this arrangement is to correct for any
drift in the output frequency of the oscillator M 25 like manner to decrease the center frequency of
the signal carrier traversing the ?rst intermedi
or in the center frequency of the received signal
carrier. In this regard, it is noted that regard
less of the settings of the tuning elements pro
vided in the tunable stages [8 and 28 of the re
ceiving channel I I, these stages are broadly tuned
to the center carrier frequency which corresponds
to the settings of the tuning elements, so that ir
respective of any drift in the center frequency
of the received carrier all modulation components
ate frequency section and increase the center
frequency of the signal carrier traversing the
scond intermediate section of the receiving chan
nel II. The resulting increase in the center ex
citation frequency of the resonant circuit 81 pro
duces a corresponding decrease in the rate of in
crease of the negative bias voltage applied be
tween the control grid and cathode of the mod
of they received signal are passed through these 35 ulator tube 38. As the bias applied to the tube
38 continues to increase at a constantly decreas
ing rate the center frequencies of the signal car
riers traversing the ?rst and second intermedi
second intermediate frequency sections of the
ate frequency sections of the receiving channel
channel I I are somewhat broadly tuned in order
to-permit, within limits, deviations in the center 40 ll change in like manner until the two factors
become balanced. It will be understood, there
carrier frequencies appearing therein without
fore, that when the received carrier frequency
cutting off the modulation components of the
is stabilized at a particular above-normal value,
frequency modulated carriers which are trans
the bias voltage applied to the modulator tube
mitted therethrough. It will be understood, there
38 is likewise stabilized at a particular value.
fore, that by providing the improved automatic
Moreover, if the circuit constants of the system
frequency control arrangement described below,
are properly chosen, this bias voltage will in each
any drift in the output frequency of the oscillator
instance be stabilized at a value such that the
M or in the center frequency of a received signal
center frequencies of the signal carriers travers
carrier is substantially corrected in so far as the
intermediate frequency sections of the receiving 50 ing the ?rst and second intermediate sections of
the receiving channel II will be held at values
channel and the discriminator 21 are concerned.
which closely approximate the center frequencies
Briefly to consider the manner in which the
at which these sections of the receiving channel
output frequency of the oscillator I4 is automat
and the discriminator 21 are designed to operate.
ically controlled, it may be assumed that the cen
If the center frequency of a selected signal
ter frequency of the received signal carrier starts 55
carrier drifts to a value below the center fre
to drift to a value higher than the center fre
quency to which the stages l8 and 20 are tuned,
quency to which the resonant circuits of the
or the output frequency of the oscillator Id drifts
tunable stages 18 and 28 are tuned, or that while
from its established value to a higher value, the
this center carrier frequency remains constant,
the output frequency of the oscillator I 4 starts 60 center frequencies of the signal carriers travers
ing the ?rst and second intermediate frequency
to drift from an established value to a lower
sections of the receiving channel I I are decreased
value. As the frequency drift starts and regard
and increased respectively. As a result, a positive
less of where it originates, the center frequency
bias voltage appears at the output side of the dis
of the carrier transmitted through the ?rst inter
mediate frequency ampli?er 22 increases to ‘pro 65 criminator 21 which is applied to the tube 38 to
duce a corresponding decrease in the center fre
produce a decrease in the output frequency of the
quency of the carrier transmited through the
oscillator l4. The center frequencies of the signal
stages of the receiving channel. In a similar
manner, the ?xed tuned stages of the ?rst and
second intermediate frequency stages 24, 25 and
26. ~As will be apparent from the above explana
tion, this departure in the exciting frequency of
the tuned circuit 8'! from the center frequency
to which this circuit is tuned, causes a bias volt
age, which is negative with respect to ground, to
be produced between the cathode of the diode 88
and ground. This bias voltage is negatively ap
carriers traversing the intermediate frequency
sections ofithe receiving channel are increased
and decreased accordingly. Thus, the frequency
correcting action proceeds in the exact manner
explained above until a point of stability is
reached at which the center frequency, of the sig
nal carrier voltage impressed upon the discrim
75 inator network 81 closely approximates the
2,408,791‘
17
81 is tuned.
'
Operation 01‘, the muting apparatus
Referring now more particularly to the manner
cutoff point.
in‘ which the audio section of the receiving chan
Accordingly, the voltage drops
across the two resistors I18 and H9 are sharply
decreased to very low values, with the result that
the fullvoltage of theavailable source of anode
nel I I is muted or squelched during periods when
the system is conditioned for operation but is not
being used either for signal transmission or re~
ception, it may be pointed out that at all times
when the system is conditioned for reception but
is not receiving a desired signal, noise signal volt~
ages appear in those stages of the receiver chan
18
grid of the tube II3 through the resistor H5.
The negative voltage appearing across the re
sistorfl In so greatly predominates over that posi
tively applied to the control grid of the tube I I3
that this tube is biased beyond its space current
center frequency to which the resonant circuit
current is positively applied to the screen elec
trode of the oscillator and recti?er tube 33. The
application of this voltage to the screen electrode
10
of the tube I'Zil initiates the operation of the I
oscillator section of this tube, so that an oscilla
nel which precede the discriminator 21. These
voltages are transmitted through the interme: ._ tory voltage is developed across the series con‘
nected coupling condenser I29 and the space
diate frequency and mixer stages of the channel
current path between the diode electrodes of the
II and are detected by the discriminator 21 to
tube. Due to the action of the diode section of
the tube I20 in rectifying the oscillatory voltage,
appear as audio frequency voltages at the output
side of the discriminator. They may be pro
duced as a result of thermal agitation within the
a direct bias voltage is produced across the diode
load circuit comprising the series resistors I23,
I32 and 181). This bias voltage is negatively ap
plied to the control grid of the ?rst tube provided
tubes provided in the receiving channel, shot
effects, extraneous noise voltages appearing across
the. antenna-ground circuit I9, or by physical
in the audio frequency ampli?er 2.8, over a path
which includesithe resistors I21 and IE0 and the
encircuited portion of the resistor 98. The mag
nitude thereof is sufficient to bias the first audio
shockto the circuit elements provided in the re
ceiving channel. Regardless of the origin‘there- ,
o__f, however, the noise signals are manifested as
audio frequency voltages across the output side
of the discriminator which, in the absence of
the muting apparatus provided in the system,
would be passed through the audio frequency
ampli?er ~23 to the loud speaker 291m repro
duction.
1
frequency ampli?er tube beyond cutoif, whereby
the‘no-ise signals are prevented from being trans
mitted through the audio channel of the receiver
to the loud speaker 29 for reproduction.
As will be apparent from further considera
_
tion of the curve shown in Fig. .4 of the draw
More speci?cally considered, the noise response
of the receiver is graphically illustrated in Fig. 4
of the drawings, wherein the noise voltage ap
pearing across the condenser 93 is plotted as a
function of the selected signal carrier input volt
age appearing across the antenna-ground circuit
L9. From a consideration of this curve, it will
be noted that when no signal carrier is being re
ceived, the noise voltage appearing at the output
side of the discriminator 21 is’ high and that the
magnitude of this voltage is sharply reduced in
response to the application of a selected signal
carrier to the antenna-ground circuit I9. The
decrease in vthe level ofthe noise voltage which
accompanies the transmission of a selected sig
nal through the receiving channel Ill, is largely
effected in the amplitude limiters 25 and 26,.’
To consider the action of the muting apparatus,
it-is pointed out that the noise voltage appear
ing between the cathode of the diode 8,8 and
35
ings, when a selected signal carrier of substan
tial magnitude appears across the antenna
ground circuit I9, the limiters 25 and 26 function
sharply to decrease the noise voltage developed
at the output side of the discriminator 21. This
produces a corresponding decrease in the bias
voltage developed across the load resistor III}.
When the negative bias applied to the control
grid of the tube I I3 is thus reduced to a low value,
the current ?ow through the resistors H8 and
lie
the space current path of the tube H3
is ‘sharply increased to produce a corresponding
increase in the voltage drops across the two
videnti?ed ~resistors. As .a result, the voltage which
is positively applied to the‘ screen electrode of
the oscillator and recti?er tube v‘3t through the
two resistors M8 and H9 is sharply decreased to
a value ‘such that operation of the oscillator sec
tion ofthig tube cannot continue. When the
ground at the output side of the discriminator
2‘! is impressed upon the input side of the high
‘production of an oscillatory voltage across the
recti?er tube I06 and appears in ampli?ed form
across the coupling condenser I08 and the diode
section of the tube I06 in series. Due to the recti
sectionof the receiving channel is rendered oper
ative to amplify the audio frequency compo
space current path of the tube I23 is thus ar
rested,the negative bias voltage across the recti
pass ?lter .39. This ?lter acts to pass only those
components of the noise voltage having fre
fier load circuit resistors 128,132 and 18b is re
duced to zero, permitting the normal negative
quencies above the normal signal‘ reproducing
bias voltage as developed across the resistor 18b
band of the receiver. For example, this ?lter may
to be impressed upon the control electrode of the
be designed to pass frequencies above 2;)‘ kilo
cycles. The noise voltage appearing across the 60 first tube provided in the audio frequency ampli
?er 28. When this ampli?er tube is thus’un
output side of the ?lter 30 is impressed between
blocked or biased to a normal value, the audio
the input electrodes of the noise ampli?er and
fying action of the diode section of the tube I06,
2. direct voltage is produced across the load re
sistor III] which varies inv magnitude in accord
ance with the magnitude of the noise voltage im
. nents of the received signal and to transmit the
same to the loud speaker .29 for reproduction,
From the foregoing explanation it will be 1.111
derstood that normally, i. e. when the system is
conditioned for signal reception, the noise sig
pressed between the input electrodes'of the tube 70 nals appearing in the receiving channel II
are utilized to completely block the audio sec
I06, This direct voltage i. e. that across there
tion of the receiving channel against the trans
sistor no, is negatively applied to the control grid
mission or noise signals to the loud speaker 29.
of the direct voltage ampli?er tube ,I~I;3 through
the resistor H2 in opposition to the ?xed ‘bias
More speci?cally, the component circuit elements
voltage normally positively applied to the control 75 of-the muting apparatus should be so chosen that
27,408,291
id
20
in the absence of a desired signal, the negative
bias voltage developed at the upper terminal of
the resistor 528 is approximately 20‘ volts. To
this end, from 40 to 50 volts must be positively
pli?er 24, and the two limiter stages 25 and 26,
.
applied to the screen electrode of the oscillator
and recti?er tube 33 when a tube of the com
mercial 1S5 type is employed in the oscillator
and recti?er stage 33. Further, the component
circuit elements of the muting apparatus should
be such that when a selected frequency modu
lated carrier is received having a magnitude ex
ceeding a predetermined low value, the voltage
positively applied to the screen electrode of the
tube £26 is dropped to approximately 20 volts
such that operation of the oscillator section of
the tube I23 is arrested. In the absence of an
to the input side of the discriminator 21, effec
tively blocks the enumerated stages of the receiv
er against the transmission of the signal modu
lated carrier which is impressed upon the input
side of the tunable radio ampli?er 20 through the
condenser 61. More particularly, the blocking
carrier voltage which appears across the output
side of the ?rst'mixer 2I in the receiver, as a re
sult of the stray capacitance coupling between
the circuit elements of this mixer and the circuit
elements associated with the crystal 58, exceeds
by several times the modulated signal carrier
which appears at the input side of the mixer 2I
due to the coupling between the transmitting
and receiving channels through the condenser
oscillatory voltage between the anode and cath
61. Since the carrier voltage as derived from
ode of this tube, the only negative bias voltage
the crystal 58 so greatly predominates over that
applied to the control grid of the ?rst tube in
transmitted through the tunable radio frequency
the audio frequency ampli?er 28 is that developed 20 ampli?er 20 to the input side of the mixer 2|,
across the grid leak resistor 1819, which voltage
those stages of the receiver which follow the
is of the order of one volt.
When the apparatus is designed to have the
characteristics just described, the audio channel
of the receiver will at all times remain blocked
during periods when a selected signal is not be
ing received and will be automatically unblocked
when a selected signal is transmitted through
the receiving channel of the system to the dis
criminator 21 ‘for detection. In this regard it
will be understood that since the high pass ?lter
30 will only pass frequencies outside of the nor
mal signal reproducing frequency band of the re
ceiving channel, the muting apparatus is not
responsive to the audio frequency components of
a received signal carrier and thus this apparatus
is prevented from blocking the audio section of
the receiving channel against the transmission
of detected signal voltages to the loud speaker 29.
Blocking the receiving channel during
mixer 2I are effectively blocked against the
transmission of the signal modulated carrier to
the discriminator 21. Thus, the loud speaker 29
is prevented from reproducing the audio fre
quency voltage developed through operation of
the microphone I2 when the system is condi
tioned for transmission.
The crystal 58 also acts in conjunction with
the ?xed tuned stages of the receiver to set the
radiated carrier center frequency so that this fre
quency cannot be changed by the discriminator
21 and is maintained at substantially the exact
desired value. Thus, due to the capacitance cou
pling between the circuit elements of the ?rst
mixer 2i and the circuit elements of the ?xed
tuned crystal 58 and resonant circuit 60, a car
rier having a frequency exactly equaling the ?rst
intermediate frequency is injected into the ?rst
intermediate frequency section of the receiving
channel' This carrier is mixed with the fre
quency produced by the oscillator section of the
In considering the manner in which the re
second mixer tube ‘I6 to produce a carrier in the
ceiving channel II is blocked against reproduc
second intermediate frequency section of the re
tion of the signal components of the modulated 45 ceiving channel which exactly equals the center
frequency to which the resonant circuit 8‘! is
carrier radiated during operation of the trans
tuned. When this carrier voltage is applied to
mission channel II, it is pointed out that the
equipment is deliberately designed and is physi
the discriminator 27, the bias voltage appearing
cally so arranged that a relatively large amount
at the output side of the discriminator between
of stray capacitance coupling exists between the 50 the lower terminal of the resistor 95 and ground
is reduced to a negligible or zero value. More
circuit elements provided in the input and out
over, since the crystal 58 and the crystal ‘I? which
put circuits of the ?rst mixer 2|, and the elec
controls the oscillator section of the second mixer
trodes of the crystal 5S and the circuit con
ductors connecting these electrodes with the in
tube 76 are invariably ?xed to oscillate at set
put electrodes of the tube 63 and the terminals
frequencies, the negligible bias voltage appearing
of the tuned circuit 52. More speci?cally, the
at the output side of the discriminator 21 can
electrodes of the crystal 58, the elements of the
not be changed or altered in the slightest degree
tuned circuit 60 and the circuit elements form
during transmission. Accordingly, the bias ap
ing the input circuit for the mixer tube ‘ID are
plied to the input electrodes, of the modulator
unshielded; and the control grid of the tube ‘I0 60 tube 38 through the resistors I3I and 31 is held
is spaced approximately one inch from the cir~
at a ?xed negligible value during transmission
cuit conductor which connects the control grid
with
the result that the modulator oscillator I3,
of the tube 63, the lower electrode of the con
I4 are in?exibly set to produce a signal modu
denser 59 and the lower electrode of the crystal
58. With this arrangement and during signal 65 lated carrier voltage having a ?xed center fre~
quency. Thus, the crystal 58, acting in conjunc
transmission, when the crystal 58 and the tuned
tion with the stages 2|, 22, 23, 24, 25, 2'5 and 21’
circuit 60 are oscillating, a strong unmodulated
of the receiving channel II, functions to stabilize
carrier voltage appears at the output side of the
?rst mixer 2I, having a frequency equal to the
the center frequency of the radiated signal car
center frequency to which the resonant circuits 70 rier at the de?nite and ?xed value desired. This
of the ?rst intermediate frequency section of
center frequency value can, however, be altered
the receiving channel are tuned. This strong‘
by adjustment of the adjusting element U to
alter the settings of the tuning elements-provided
carrier voltage as transmitted through the ?rst
intermediate frequency ampli?er 22, the second
in the tunable stages I4, I5, I6, I‘! and I8 of the
mixer 23, the second intermediate frequency vam 75 transmission channel, but-once the desired value
transmission
2,408,791
is established it is maintained by the crystal 58
in the manner just explained.
a
-
Within the true spirit and‘ scope of the invention.
I claim:
'
'
‘
~
7
1. In a frequency modulated radio transmit
The strong carrier. injected by the'crystal 58
ting and. receivingsystem which-includes means
intermediate frequency channel of: the receiving UK for ‘selectively conditioning the system for signal
transmission orreception, avreceiving channel
channel ll through the capacitance couplingbe»
and its associated circuit elements into the ?rst
including a mixer’ stage followed by» an inter
mediate frequency section, a transmission chan
crystal‘ 58v and the circuit elementsofi the ?rst
nel-‘including a carrieriproducing oscillator 'cou
mixer 2|,also serves to control the muting appa
ratusl so that the audio section 28. of the receivingr 10 pledv to said mixer stage to operate as a local
oscillator during signal reception, and inversely
channel I l is unblocked or rendered active during
acting
means coupled betweenv said intermediate
signal transmission. More speci?cally, this car
frequency channel and said oscillator for auto
rier has the same effect, in so far as the reduction
matically controlling the output frequency of‘said
of noise voltages at the output side of the dis
oscillator to hold, substantially constant the center
15
criminator 21 is concerned,- as does the ‘applica
frequency of a frequency modulated carrier trans
tion of a strong signal of a selected center carrier
mitted through the intermediate frequency sec
frequency to the antennaground circuit I9. Ac
tion of said receiving channel during signal
cordingly, and as will be apparent by reconsider
reception.
ing the curve‘ shown in’ Fig. 4 of the drawings,
tween the circuit elements ‘associated with the
2. In a combined radio transmitting and re
when the strong carrier is injected'into the ?rst
intermediate frequency section of the receiving
channel, the noise voltage developed between the
cathode of the tube 88 and ground at the output
side of the discriminator 21 drops to a negligible
As a result, the oscillator section of the
tube I23 stops oscillating, for reasons explained
above, and the negative blocking bias isremoved
from the control grid of the'?rst tube in the audio
ceiving system which includes means for selec
tively conditioning the system for signal trans-'
mission or reception, a receiving, channel in
cluding a mixer stage followed by an inter
mediate frequency section, a1 transmission‘ chan
nel including a carrier producing oscillator cou
value.
. pled to said mixer stage to operate as a'local
oscillator during signal reception, and inversely
acting means coupled between said intermediate
frequency ampli?er 28. Thus, this amplifier is
frequency channel and said oscillator for auto
matically controlling the output frequency- of
said oscillator to hold substantially constant the
carrier frequency of a signal modulated carrier
transmitted through they intermediate frequency
rendered operative, and may, if desired, be used
to amplify and transmit to the loud‘ speaker 29
for reproduction, any side tone voltage suitably
derived from the audio channel of the trans
mission channel I0;
section of saidreceiving channel during signal
From the foregoing explanation it will be ap
parent that an improved system is provided in
which all available tubes and circuit elements
reception.
are utilized with maximum effectiveness both dur
ing reception and transmission. ’ Thus, the master
oscillator I4 is not only used as a carrier pro-l
transmission ‘or reception, a receiving channel
including a mixer stage‘ followedby an interme
ducing oscillator during’ signal’ transmission, but
is also coupled to the ?rst mixer stage 2 l‘ to oper
ate as a local oscillator during reception. Again
the modulator stage I3 is not only used'ito ireacé
tively modulate the carrier output of the oscil
lator 54 during transmission but, in addition,
diate frequency section and a frequency discrim
inator in the order named, a transmission'channel
including a modulator and an oscillator controlled
’ by said modulator to produce a frequency modu
functions to provide automatic frequency control
in the intermediate frequency sections of the
receiving channel during signal reception. The -50
use ‘of the transmitter stages l3, !4 and‘ [5 in the
dual capacities mentioned may be directly at
tributed .to the provision of the mixer‘ stage V5
in the transmission channel in. Thus by provid
ing at this ‘stage a mixing oscillator having ‘an
'
3..In a frequency modulated radio transmit
ting and receiving system which includesv means
for selectively conditioning the system for signal
lated carrier during signal transmission, means
coupling said oscillator to said mixer stage to
operate as a local oscillator during signal recep
tion, and means coupling the output side of said
discriminator to said modulator'to govern the
output frequency of said oscilator so that-the
center frequency of a frequency modulated car
rier transmitted? through the intermediate fre
quency section of said receiving channel during
reception is held substantially constant. e
output frequency equaling the center'frequency 55 signal
‘4. In a frequency modulated radio transmit
of the ?rst intermediate frequency. section of the
ting and receiving system which includes means
receiving channel, it becomes practical to utilize
for selectively conditioning the system for'signal
the three stages 13, 14' and [5 of the system in,
transmission or‘ reception; a receivingchannel
‘the dual capacities indicated. This is true for 60 including a mixer stage followed by an interme
the reason that by providing the mixing oscillator
diate frequency section and a frequency discrimi
at the mixer stage I6, transmission and reception
nator in the order named, a transmission channel
may be effected at the same center carrier fre
including an oscillator coupled to said mixer stage
quency without in any way altering the tuning
of any of the tunable stages of the system as it is
to operate as a local oscillator during signal re
65 ception, and means controlled by said discrimi
nator for automatically controlling the output
selectively conditioned for signal transmission
frequency of said oscillator to hold substantially
constant the center frequency of a frequency
modulated carrier transmitted through the in
mission mixer l6 and the power ampli?er II are
required to be controlled in order selectively to 70 termediate frequency section of said receiving
channel during signal reception.
condition the‘system for signal transmission or
or reception. Moreover, by providing the de
scribed novel system arrangement, only the trans
reception.
5. In a combined radio transmitting and re
ceiving system which is adapted to be selective
ly conditioned for signal transmission or signal
While one embodiment of the invention has
been disclosed, it will be understood that various
modi?cations may be made therein, which are‘ 75 reception, transmission and. receiving channels
23
2,408,791
24
respectively including high frequency carrier and
intermediate frequency carrier sections, two like
sections of said channels including frequency se
lective stages which are tuned to the same reso
nant frequencies, frequency converters respec
tively provided in said channels at the junctions
between the high and intermediate frequency
sections thereof, means coupling the intermedi
ate frequency section of said transmission chan
nel to the frequency converter of said receiving 10
channel so that a frequency beating carrier is
supplied to said last-named frequency converter
from said transmission channel during signal re
ception, and means for rendering the high fre
quency section of said transmission channel in
active when said system is conditioned for sig
nal reception.
of the intermediate frequency section of said
transmission channel is‘ equal to the difference
between the center resonant frequencies of the
radio and intermediate frequency sections of said
receiving channel, a coupling path for injecting
a carrier voltage into said converter from said
one stage of said transmission channel during
signal reception, and means for rendering the
radio frequency section of said transmission chan
nel inactive when said system is conditioned for
ignal reception.
8. In a combined radio transmitting and re~
‘ceiving system which is adapted to be selective~
ly conditioned for signal transmissionor signal
15 reception; a transmission channel provided with
a modulator, a carrier producing oscilator, a tun
able frequency doubler, a tunable mixer stage
6. In a combined radio transmitting and re
and a tunable radio frequency section connected
ceiving system which is adapted to be selective
in tandem in the order named; a receiving chan
ly conditioned for signal transmission‘ or signal 20 nel provided with a tunable radio frequency sec—
reception, a transmission channel provided with
tion, a tunable mixer stage, an intermediate fre
an audio frequency section, a tunable interme
diate frequency section and a tunable radio fre
quency section in the order named, a receiving
quency section and a frequency discriminator con
nected in tandem in the order named; means for
said one stage of said transmission channel dur
tion, a tunable mixer stage, an intermediate fre
quency section and a frequency discriminator
connected in tandem in the order named; means
for utilizing the carrier voltage developed at the
output side of said doubler as a local oscillator
utilizing the carrier voltage developed at the out
channel provided with a tunable radio frequency 25 put side of said doubler as a local oscillator volt
section, an intermediate frequency section and
age for frequency conversion at the mixer stage
an audio frequency section in the order named,
of said receiving channel during signal reception,
a frequency converter provided between the radio
tuning elements respectively provided in said tun
and intermediate frequency sections of said re
able stages, and unicontrol means for so control
ceiving channel, tuning elements respectively pro 30 ling said tuning elements that regardless of the
vided in said tunable stages, and unicontrol means
settings of said tuning elements the center reso
for controlling said tuning elements so that re
nant frequencies of said radio frequency sections
gardless of the settings of said tuning elements
are substantially equal.
the center resonant frequencies of said radio fre
9. In a combined radio transmitting and re
quency sections are substantially equal and the 35 ceiving system which is adapted to be selectively
center resonant frequency of at least one stage
conditioned for signal transmission or signal re
of the intermediate frequency section of said
ception; a transmission channel provided with
transmission channel is equal to the difference
a. modulator, a carrier producing oscillator, a tun
between the center resonant frequencies of the
able frequency doubler, a tunable mixer stage
radio and intermediate frequency sections of said 440 and a tunable radio frequency section connected
receiving channel, and a coupling path for in
in tandem in the order named; a receiving chan
jecting a carrier voltage into said converter from
nel provided with a tunable radio frequency sec
ing signal reception.
. '7. In a combined radio transmitting and receiv
ing system which is adapted to be selectively
conditioned for signal transmission or signal re
ception, a transmission channel provided with an
voltage for frequency conversion at the mixer
audio frequency section, a tunable intermediate
stage of said receiving channel during signal re
frequency section and a tunable radio frequency 50 ception, tuning elements respectively provided in
section in the order named, a receiving channel
said tunable stages, unicontrol means for so con
provided with a tunable radio frequency section,
trolling said tuning elements that regardless of
an intermediate frequency section and an audio
the settings of said tuning elements the center
frequency section in the order named, a fre
resonant frequencies of said radio frequency sec
quency converter provided between the radio and
tions are substantially equal, and means cou
intermediate frequency sections of said receiv
pling the output side of said discriminator to said
ing channel, tuning elements respectively provided
modulator to govern the output frequency of said
in said tunable stages, and unicontrol means for
oscillator so that the carrier frequency of a sig
controlling said tuning elements so that regard
nal modulated carrier transmitted through the
less of the settings of said tuning elements the 60 intermediate frequency section of said receiving
center resonant frequencies of said radio fre
channel is held substantially constant.
quency sections are substantially'equal and the
center resonant frequency of at least one stage
HENRY MAGNUSKI.
Документ
Категория
Без категории
Просмотров
0
Размер файла
2 413 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа